1. Field of Invention
This invention related to holography, and particularly to a novel method for producing holographic stereogram images from a sequential series of two dimensional images generated on an Liquid Crystal Display (LCD) matrix.
2. Prior Art
In order to provide background information so that the invention may be completely understood and appreciated in its proper context, reference is made to a number of prior art patents and publications as follows:
Benton U.S. Pat. No. 4,445,749 "Holographic Products and Processes".
An article by D. J. DeBitetto entitled Holographic Panoramic Stereograms Synthesized from White Light Recording, appearing on pages 1740 and 1741 of Applied Optics, Volume 8, No. 8 Aug. 1969.
An article by S. A. Benton , D. A. Duston-Roberge and R. Simard entitled "Achromatic holographic stereogram of Landsat Multispectral scanner data." Appearing on pages 338, 339 and 340 of Optical Engineering Vol. 24, No. 2, Mar.-Apr. 1985.
An article by King, Noll, and Berry, entitled "A New Approach to Computer Generated Holography published in Applied Optics pages 471-475. Vol. 9, No. 2 Feb. 1970.
The basic process of generating holographic stereograms is described by Benton U.S. Pat. No. 4,445,749, I quote "beginning with the step of recording a series of two dimensional photographs of three dimensional subject taken from a series of equally spaced positions along a horizontal line. Images from these photographs are subsequently projected on a translucent screen. As each of the series of images is projected, it is holographically recorded on a region of a stationary photographic plate exposed by a horizontally movable vertical slit aperture, such that the images are recorded as a sequence of vertical strips on the photographic plate. Upon illumination of the strip hologram so produced with monochromatic light, a three-dimensional image is produced that has horizontal parallax but not vertical parallax."
Whatever the precise merits, features and advantages of the above cited references, none of them achieves or fulfills the purpose of the present invention.
Two major problems are encountered when making stereograhic holograms using transparent film, specifically vibration and image registration.
Vibration when recording a hologram prevents the hologram from being recorded properly, thereby making the image useless. Improper registration of images would also make the subsequent stereographic hologram useless. Vibration is caused by the equipment that sequentially steps the transparent film images. And precise registration of the images along its vertical and horizonal axis such that one image is in proper register with the next and so forth for all the images required is a tedious procedure.
The Vertal slit aperture that moves horizontally so that the images are recorded as a sequence of vertical holographic strip images is still another cause vibration and alignment problems. In some systems, the aperture remains fixed while the holographic plate behind it moves, in either system vibration is generated.
Vibration is currently handled by allowing the systemn to stablize to a non-vibration state after each exposure which includes moving the vertical slit aperture to its next position and advanceing the transparency film to the next sequential image. The laser is either de-energized or shuttered in an off position during the time the system is stablizing.
In addition computer generated sequential images that are rotated about a vertical axis must include an intermediate step of first being recorded sequentially onto transparent film.